1. Field of the Invention
The present invention relates to a distance measuring apparatus and, more particularly, to a distance measuring apparatus for measuring a distance to an object to be photographed, based on an optical image which is formed by divided object light beams.
2. Description of the Related Art
In a scene in which a person is photographed by setting a night view to the background, portions having a high luminance exist only in the background of the screen. The person as a main object is photographed almost in a dark-compressed state.
When photographing such a scene by an automatic focusing camera or the like, a distance is measured and a focus is controlled on the basis of a subject whose luminance is high at the background. This might cause a danger that although the user desires to make the person in-focus, the background is erroneously made in-focus.
In order to improve the foregoing, as disclosed in, e.g., Japanese Patent Publication No. 7-199039, auxiliary light is accurately turned on at a night view photographing mode and thus a main object to be photographed is illuminated, thereby detecting an in-focus point to the main object.
As disclosed in, e.g., Japanese Patent Publication No. 9-5611 as another technique, there is provided a distance measuring apparatus for measuring a distance by an active system and a passive system, wherein the distance measurement based on the passive system is inhibited and the distance measurement based on the active system is executed at a night view photographing mode, thereby detecting an in-focus point to a main object.
However, the use of the above-mentioned technique disclosed in Japanese Patent Publication No. 7-199039 does not necessarily provide a suffient effect.
That is, the limit of an arranging space makes it difficult to utilize a light source which emits a sufficiently large quantity of light in an auxiliary light emitting device which is built in a camera. Thus, reflectance might be low, depending on an object. The aforementioned and the like might cause a remarkable decrease in light quantity which is reflected by the main object, and there are many cases where the light quantity is insufficient to clearly photograph a person or the like as a main object from among the background, and it is impossible to measure a distance accurately.
It is possible to devise means for irradiating a full quantity of light to the main object by reducing a distance between a camera and an object so as to accurately measure the distance by employing the auxiliary light. However, if the main object is near, the distance measuring area includes no portion having a high luminance in the background, and an erroneous operation for measuring the distance itself is not executed.
In accordance with the above-discussed technique disclosed in Japanese Patent Publication No. 9-5611, a distance measuring apparatus using a plurality of systems is made necessary. Therefore, not only are costs increased, but also a camera provided with the distance measuring apparatus has a larger size.
Thus using the above-described related art, the problems on erroneous distance measurement cannot be fully solved or it is necessary to waste costs and space so as to improve the distance measuring performance.
It is an object of the present invention to provide a distance measuring apparatus which is inexpensive and has a small size, wherein a distance measuring value is prevented from largely deviating from a main object even for a scene of a night view or a view based on a night view as a background.
In brief, according to the present invention, there is provided a distance measuring apparatus comprising: light receiving means of a charge accumulating type, having a plurality of pixels, for light-receiving optical images which are formed by light beams of an object to be photographed which are divided into at least one pair and outputting a signal of an object image; distance measuring means for outputting distance information regarding a distance to the object, based on an output by the light receiving means; night view discriminating means for discriminating whether or not a photographing object situation is a night view or a view in which a night view is a background, based on a result to detect whether or not a mode is set and operated to a night view photographing mode by a manual operating member or a result to calculate the output by the light receiving means; and correcting means for outputting a correct value to correct an output by the distance measuring means to a predetermined direction when the night view discriminating means determines that the photographing object situation is the night view or the view in which the night view is the background and the output by the distance measuring means is equal to or greater than a predetermined distance.
According to the present invention, there is also provided a distance measuring apparatus for image-forming light from an object to be photographed on at least one pair of photoelectric converting element arrays through at least one pair of light receiving means and calculating an object distance from at least two object image signals obtained, comprising: distance discriminating means for discriminating whether or not the object distance as a distance measuring result is shorter or longer than a first predetermined distance; night view discriminating means for discriminating whether or not the object is based on a night view or a view in which a night view is a background; and distance measuring result changing means for changing and setting the object distance as the distance measuring result to a second predetermined distance when the distance discriminating means determines that the object distance is longer than the first predetermined distance and the night view discriminating means determines that the object is based on the night view or the view in which the night view is the background.
Further, according to the present invention, there is provided a distance measuring means in a camera for receiving light from an object by light receiving means, obtaining an object image signal, and controlling a focus on the basis of the obtained object image signal, comprising: in-focus distance predicting means for predicting an absolute position of an in-focus distance of a focus control optical system after in-focus driving from a focus detecting result, and predicting whether or not the absolute position is within a predetermined range; night view discriminating means for discriminating whether or not the object is based on a night view or a view in which a night view is a background; and focus control correcting means for correcting the in-focus distance to a predetermined drive quantity to be shorter than the predetermined range when the in-focus distance predicting means determines that the in-focus distance is within the predetermined range and the night view discriminating means determines that the object is based on the night view or the view in which the night view is the background.
These object and advantages of the present invention will become further apparent from the following detailed explanation.